import pandas as pd
df=pd.DataFrame({
    '商品':['苹果','香蕉','梨'],
    '单价（元）':[5,5,4],
    '销量（kg）':[100,None,None],
    '库存（kg）':[50,None,70]
})
print('原始数据:\n',df)
print('删除包含缺失值的行:\n',df.dropna())
print('删除包含缺失值的列:\n',df.dropna(axis=1))
print('删除少于3个非缺失值的行:\n',df.dropna(thresh=3))
print('删除库存列包含缺失值的行:\n',df.dropna(subset=['库存(kg)']))